1. Field of the Invention
The present invention relates generally to the composition of panels employed as building materials in the construction of the surfaces of buildings and methods related to the manufacture of the panels. In particular, the present invention concerns the composition and manufacture of fire-resistant panels employed as ceiling tiles in ceiling suspension systems.
2. Discussion of the Prior Art
It is often the case that the walls and ceilings of buildings are constructed using pre-manufactured panels, such as: wallboard, including gypsum board for example; cement board including Durock® for example; and ceiling tile. The panels are self-supporting in that each panel is capable of supporting its own weight and retaining its shape without the assistance of reinforcing means or techniques. For example, in those instances in which the panels comprise ceiling tiles that are employed in a ceiling suspension system, the ceiling suspension system can comprise a system of metal or plastic members, referred to in the art as “tee” section elements, that are spaced apart in a grid-like arrangement that provides openings in which the ceiling tile can be suspended.
The composition or make-up of the pre-manufactured panels can vary widely. For example, the panels can comprise a base mat or core that includes, in varying amounts, one or more materials such as a gypsum-based material, mineral wool, fiberglass, cellulose fibers, clay, starch and perlite for example. In some instances, the panels can include a facing material, such as a vinyl material for example, attached to one or both sides of the base mat.
Typically, the perlite that is included in pre-manufactured panels comprises expanded perlite. Expanded perlite can be produced by subjecting ground perlite ore to an expansion operation wherein the ground perlite ore is expanded into coarse, medium and fine expanded perlite particles many times greater in size than the ground perlite ore from which the expanded perlite particles have been produced. The compositions of the panels, both with respect to the materials and the relative amounts of the materials the panels include, can be influenced by the properties it is intended that the panels possess. For example, panels that are intended to have special acoustical properties, typically, can be composed of materials and amounts thereof that are different from the materials and amounts of the materials that are included in panels whose acoustical properties are of no great concern. Similarly, the compositions of ceiling tiles that are to be installed in a high-humidity environment can be engineered to provide greater than normal resistance to the effects of moisture-laden air.
In certain instances, it can be important that the ceiling tiles be highly resistant to fire. Ceiling tile systems can be designed so as to form a membrane to prevent the fire from escaping through the ceiling and spreading. In order for the integrity of the membrane to be maintained, it is important that the ceiling tiles upon being exposed to the heat generated by a fire not sag or slump or be consumed to an extent that the ceiling tiles fall from the openings in the suspension system at which the tiles are supported. Special formulations can be employed in the manufacture of the ceiling tiles so as to prevent undue destruction of the tile when the tile is exposed to heat, including open flames.